28 BULLETIN 314, tJ. S. DEPAETMENT OF AGEICULTUEE. 



than 15 minutes is necessary, and the following method proposed by 

 the Committee on Standard Tests for Road Materials of the American 

 Society for Testing Materials is recommended: x 



From 2 to 15 grams (depending on the richness in bitumen of the substance) is 

 weighed into a 150-cubic centimeter Erlenmeyer flask, the tare of ■which has been 

 previously ascertained, and treated with 100 cubic centimeters of carbon disnlphide. 

 The flask is then loosely corked and shaken from time to time until practically all 

 large particles of the material have been broken up, when it is set aside and not dis- 

 turbed for 48 hours. The solution is then decanted off into a similar flask that has 

 been previously weighed, as much of the solvent being poured off as possible without 

 disturbing the residue. The first flask is again treated with fresh carbon disulphide 

 and shaken as before, when it is put away with the second flask and not disturbed for 

 48 hours. 



At the end of this time the contents of the two flasks are carefully decanted off 

 upon a weighed Gooch crucible fitted with an asbestos filter, the contents of the sec- 

 ond flask being passed through the filter first. The asbestos filter shall be made of 

 ignited long-fiber amphibole, packed in the bottom of a Gooch crucible to the depth 

 of not over one-eighth of an inch. After passing the contents of both flasks through 

 the filter, the two residues are shaken with more fresh carbon disulphide and set aside 

 for 24 hours without disturbing, or until it is seen that a good subsidation has taken 

 place, when the solvent is again decanted off upon the filter. This washing is con- 

 tinued until the filtrate or washings are practically colorless. 



The crucible and both flasks are then dried at 125° C. and weighed. The filtrate 

 containing the bitumen is evaporated, the bituminous residue burned, and the 

 weight of the ash thus obtained added to that of the residue in the two flasks and the 

 crucible. The sum of these weights deducted from the weight of substance taken 

 gives the weight of bitumen extracted . 



USE OF TOTAL BITUMEN DETERMINATION. 



This determination is made on all classes of bituminous products. 

 In the analysis of tars the organic matter insoluble is commonly 

 known and reported as ''free carbon." 



DETERMINATION OF BITUMEN INSOLUBLE IN PARAFFIN NAPHTHA. 



EQUIPMENT. 



The apparatus is the same as for bitumen soluble in carbon disulphide. 



This determination is made in the same general manner as the 

 total bitumen determination, except that 100 cubic centimeters of 

 88° to 88° B. paraffin naphtha, at least 85 per cent distilling be- 

 tween 35° C. and 65° C, is employed as a solvent instead of carbon 

 disulphide. Considerable difficulty is sometimes experienced in 

 breaking up some of the heavy semisolid bitumens; the surface of the 

 material is attacked, but it is necessary to remove some of the 

 insoluble matter in order to expose fresh material to the action of 

 the solvent. It is, therefore, advisable to heat the sample after it is 

 weighed, allowing it to cool in a thin layer around the lower part of 



1 Proc. Am. Soc. for Testing Materials, 1909, Vol. IX, p. 221. 



